Длина строки до 100 символов является допустимой.

http://hg.python.org/peps/rev/fb24c80e9afb

Уху +20

+For flowing long blocks of text with fewer structural restrictions
1.110 +(docstrings or comments), limiting the line length to 72 characters
1.111 +is recommended.
1.112 +
1.113 +Limiting the required editor window width makes it possible to have
1.114 +several files open side-by-side, and works well when using code
1.115 +review tools that present the two versions in adjacent columns.
1.116 +
1.117 +The default wrapping in most tools disrupts the visual structure of the
1.118 +code, making it more difficult to understand. The limits are chosen to
1.119 +avoid wrapping in editors with the window width set to 80 (or 100), even
1.120 +if the tool places a marker glyph in the final column when wrapping
1.121 +lines. Some web based tools may not offer dynamic line wrapping at all.
1.122

“Ух ты, так я оказывается придерживаюсь PEP8!” - промелькнуло в головах у разработчиков. : )